The present invention relates to a process for obtaining purified phosphatidylcholine. The present invention in particular relates to a method for obtaining purified phosphatidylcholine which produces a mixture of glycerides as well. In another aspect, the present invention relates to a process for obtaining purified phosphatidylcholine from a raw lecithin gum.
In the fats and oils industry, the term "lecithin" is used to refer to a mixture of phosphatides that may include phosphatidylcholine (PC), phosphatidylethanolamine (PE) phosphatidylinositol (PI), phosphatidylserine (PS) phosphatidic acid (PA) and others. In the scientific literature, the term lecithin has been used to refer to PC, and the term "cephalin" has been used to refer to PE and mixtures of PE and the non-choline phosphatides. The industry use of the term lecithin is applied herein, and names for specific phosphatides (e.g. PC, PE, etc.) will be used as appropriate except when other patents and literature are quoted.
Processes for the separation of lecithin from contaminating substances are well known in the art. For example, see, Szuhaj, B.F. (ed.) Lecithins, American Oil Chemist's Society, Champaign, Ill. 1989. Recognition of the unique properties and possible uses of individual phosphatide components of lecithin, particularly PC, and the adverse effects in certain applications of contaminating non-choline phosphatides in PC enriched fractions, has stimulated the search for improved methods of PC purification from lecithin.
There are many known methods for obtaining purified phosphatidylcholines from various starting materials. For example, German Patent No. 1,617,679 discloses a process to obtain highly purified phosphatidylcholine with a high content of essential fatty acids from plant lecithins by adsorption of the phosphatides on aluminum oxide and extraction with alcohol. This process is characterized in that the raw oil phosphatides are dissolved in ethyl acetate or a dichlorinated hydrocarbon having 1 to 2 carbon atoms or in mixtures of these solvents. The solvent can contain up to 6% by volume of alcohol. The solution is then treated, with stirring, with at least five-fold amount of aluminum oxide relative to the content of raw phosphatide. Finally, the highly purified phosphatidylcholine is liberated with alcohol from the separated aluminum oxide. According to German Patent No. 1,617,680 the solution of the oily raw phosphatide solution is contacted with an aluminum oxide column (instead of stirring therewith) and the chemically pure phosphatidylcholine is liberated from the aluminum oxide adsorbent with alcohol.
Swiss Patent No. 561,088 and U.S. Pat. No. 2,945,869 describe purification processes to obtain soya phosphatide fractions to be used as emulsifiers for aliphatic emulsions designed for intravenous application. Alcoholic solutions of previously deoiled raw phosphatides are treated according to these processes with Al.sub.2 O.sub.3, MgO or activated charcoal, respectively, in order to make these solutions poor in cephalin and, primarily to remove from these solutions most of the inositol-containing phosphatides which were found to lower the blood pressure in cats when introduced intravenously.
However, this latter process always requires a previous deoiling of the commercially available raw phosphatides prior to the preparation of the alcohol solutions which will only lead to a reduction in the cephalin content, regardless of the absorbent being used. A more extensive or complete removal of the cephalin cannot be accomplished by this known process.
German Patent No. 1,053,299 discloses a process to obtain natural choline phosphoric acid diglyceride esters which are free of colamin phosphoric acid diglyceride esters, by use of column chromatography where aluminum oxide is used, among other substances, as the absorbent. This process again uses an alcoholic extract of the previously deoiled raw phosphatide, with the prior deoiling accomplished by repeated extractions with acetone.
In the case of the processes disclosed by German Patent Nos. 1,617,679 and 1,617,680, the oily raw phosphatide mixtures are dissolved in ethyl acetate or a chlorinated hydrocarbon without prior deoiling, and these solutions are then treated with aluminum oxide. Deoiling of the raw phosphatides occurs while all phosphatides will remain at the adsorbent. The phosphatidylcholine can then be selectively liberated by treating the aluminum oxide with an alcohol. Highly purified oil-free phosphatidylcholines can be obtained by means of this process.
U.S. Pat. No. 3,798,246 discloses purifying the crude phosphatides recovered from soybean oil by contacting a hexane solution of the crude phosphatides with activated silica gel for at least 20 minutes, separating the silica gel from the solution, and evaporating the solvent.
U.S. Pat. No. 3,869,482 discloses a method for producing highly purified phosphatides from the total lipoid extract of animal organs. The process comprises first completely freeing a total lipoid extract of proteins by a solvent treatment. The extract is then washed to remove water soluble impurities and subjected to an absorption process for separating the other phosphorus-free lipoids.
U.S. Pat. No. 4,166,823 discloses a process for purifying phosphatides in order to obtain transparent phosphatides. The process involves subjecting crude phosphatides to the combined action of a hydrophobic liquid and water. The two liquids are separated and the purified phosphatide product is recovered from the hydrophobic liquid.
U.S. Pat. No. 4,235,793 discloses a process wherein raw lecithins are first extracted with a lower alcohol of 1 to 3 carbon atoms. The resulting two phases are separated and the alcohol-rich upper phase is treated with an aluminum oxide adsorbent. Elution of the adsorbent with an alcohol results in an oily phosphatidylcholine, free of cephalin and inositol phosphatides.
U.S. Pat. No. 4,443,378 discloses a process for the separation of acylated phospholipids. The process utilizes chromatography on silicic acid gel in a lower alkanol containing 1 to 4 carbon atoms as solvent and/or eluant.
U.S. Pat. No. 4,452,743 discloses a process for the separation of oil and/or phosphatidylethanolamine from alcohol soluble phosphatidylcholine products containing the same. This process also utilizes chromatography on silicic acid gel in a lower alkanol containing 1 to 4 carbon atoms as solvent and/or eluent.
U.S. Pat. No. 4,528,139 discloses a process for the preparation of phosphatide fractions highly enriched with phosphatidylcholine by warming an ethanolic extract of deoiled crude phosphatides at elevated temperatures before the addition of aluminum oxide and containing intensive stirring at elevated temperatures until the equilibrium saturation concentration is established.
Other publications which relate to the purification of phosphatidylcholine, phosphatide products or phosphatidylcholine products include British Patent No. 1,292,774; "Phosphatidylcholine Transfer Protein from Rat Liver: Purification and Radioimmunoassay" by Tuerlink et al Method in Enzymology, 1983, vol. 98, pp. 586-92; "Large Scale Purification of Phosphatidylcholine From Egg Yolk Phospholipids by Column Chromatography on Hydroglapatite." by Primes et al, Journal of Chromatography, 1982, vol. 236, No. 2, pp. 519-22; Journal of Lipid Research, 1977, vol. 18, No. 6, pp. 704-9; and, Physiologie Vegetale, "Rapid Preparation of Highly Purified Phosphatidylcholine By High-Performance-Liquid Chromatography" vol 24 No 5, (1986) pp. 597-605.
Generally, the processes described above result in fractions that are "enriched" in phosphatidylcholine rather than containing "purified" phosphatidylcholine in the context of being free of contaminating non-choline phosphatides. The costliness and efficiency of such processes depend upon the purity of the starting material. If a raw starting material is used, this may decrease the material cost of the process, but increase the actual processing cost because of the undesirable components. In general, the costliness of the present commercial process is high. New processes for the purification of phosphatidylcholine are therefore continuing to be developed in the hope of providing a process which is easier and more cost effective.
Therefore, it is an object of the present invention to provide a novel process for removing non-choline phosphatides from a raw material containing same which facilitates obtaining highly purified phosphatidylcholine.
Another object of the present invention is to provide a process for effectively obtaining a highly purified phosphatidylcholine product, particularly from a raw gum material.
It is another object of the present invention to provide such a process which is cost effective and easily manipulated.
These and other objects of the present invention will become apparent upon a review of the following description and the claims appended hereto.